DESCRIPTION (from the investigator's abstract): Cortical processing of visual motion has emerges as a model system for studying the relationship between neural activity and perception. Knowledge of cortical processing stages, relevant perceptual phenomena and computational strategies for motion processing is now sufficiently well- established to permit facile exploration of their interrelations. A series of coordinated neurophysiological and psychophysical experiments has been designed with this aim. This project will initially focus on cortical visual areas MT. Emphasis will be placed upon obtaining evidence for direct links between neural and perceptual events, through neurophysiological recording in conscious behaving animals. Spatiotemporal context is essential for the detection and perceptual interpretation of retinal image motion. This implies a specific functional role for crosstalk between visual sub-systems, such as those devoted to motion, color, and depth. Studies have been designed to explore the ways in which contextual information carried by sub-system interactions can reveal figure/ground relationships and can thus facilitate detection of motion. Psychophysical experiments will be used to reveal relevant contextual effects, and neurophysiological experiments will be used to identify neural correlates and explore underlying mechanisms. Behavioral context also influences perception of image motion. For example, motion detection in the presence of visual noise can be markedly enhanced by attentional tracking. The engagement of attention-based motion detection is tied to behavioral goals, and is likely to play a significant role in normal visual perception. Nothing is currently known of its neural bases. Coordinated psychophysical and neurophysiological experiments have been designed to identify neural structures and events that underlie this perceptual phenomenon. Lastly, a very basic question concerns the role of cortical motion detectors in perceptual sensitivity to spatial contrast. Many psychophysical studies have suggested that contrast sensitivity is limited by the sensitivity of directionally selective neurons. A classical psychophysical procedure will be adapted to neurophysiological studies in an effort to evaluate this long-standing hypothesis. The long-term goal of this project is to contribute to the understanding of biological substrates of visual perception and visually-guided behavior. Information obtained will ultimately aid in the treatment and prevention of neurologic and ophthalmic disorders of vision caused by trauma, disease and developmental defects. The aims are pertinent to a variety of clinical applications including the development of visual prostheses and treatment programs for perceptual deficits.